5h 26min, may 8, 1820 y - Missouri Compromise
Description:
 The Missouri Compromise was an effort by Congress to defuse the sectional and political rivalries triggered by the request of Missouri late in 1819 for admission as a state in which slavery would be permitted. At the time, the United States contained twenty-two states, evenly divided between slave and free. 
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Date:
5h 26min, may 8, 1820 y
Now
 ~ 205 years ago